Commit | Line | Data |
---|---|---|
eb676f2b BJ |
1 | .TH READ 2 |
2 | .SH NAME | |
3 | read \- read from file | |
4 | .SH SYNOPSIS | |
5 | .B read(fildes, buffer, nbytes) | |
6 | .br | |
7 | .B char *buffer; | |
8 | .SH DESCRIPTION | |
9 | A file descriptor is a word | |
10 | returned from a successful | |
11 | .I "open, creat, dup," | |
12 | or | |
13 | .I pipe | |
14 | call. | |
15 | .I Buffer | |
16 | is the location of | |
17 | .I nbytes | |
18 | contiguous | |
19 | bytes into which the input will be placed. | |
20 | It is not guaranteed | |
21 | that all | |
22 | .I nbytes | |
23 | bytes will be read; for example | |
24 | if the file refers to a typewriter at most one line | |
25 | will be returned. | |
26 | In any event the number of characters read is returned. | |
27 | .PP | |
28 | If the returned value is 0, then | |
29 | end-of-file has been reached. | |
30 | .PP | |
31 | If very large data files are to be accessed randomly, see | |
32 | .I vread (2) | |
33 | .SH "SEE ALSO" | |
34 | open(2), creat(2), dup(2), pipe(2), vread(2) | |
35 | .SH DIAGNOSTICS | |
36 | As mentioned, | |
37 | 0 is returned when the end of the file has been reached. | |
38 | If the read was otherwise unsuccessful | |
39 | the return value is \-1. | |
40 | Many conditions | |
41 | can generate an error: | |
42 | physical I/O errors, bad buffer address, | |
43 | preposterous | |
44 | .I nbytes, | |
45 | file descriptor not that of | |
46 | an input file. | |
47 | .SH "ASSEMBLER (PDP-11)" | |
48 | (read = 3.) | |
49 | .br | |
50 | (file descriptor in r0) | |
51 | .br | |
52 | .B sys read; buffer; nbytes | |
53 | .br | |
54 | (byte count in r0) |